1. Field of the Invention
This invention relates to a clip apparatus for ligaturing a living tissue.
2. Description of the Related Art
Each of Jpn. Pat. Appln. KOKAI Publication Nos. 2002-191609 and 2004-121485 discloses a clip apparatus for ligaturing a living tissue comprising: an insertion part which is to be inserted into a forceps channel of an endoscope inserted into a body cavity of a living thing; a clip unit which includes a clip provided removably at a distal end portion of the insertion part and configured to be opened and closed; and a clip operating part which includes an external operation portion exposed at a proximal end portion of the insertion part and a clip connecting portion extending from the external operation portion to the distal end portion in the insertion part and connected to the clip unit, and which is configured to open and close the clip of the clip unit by operating the external operating portion.
Such conventional clip apparatus for ligaturing a living tissue will be explained hereinafter with reference to FIG. 5 to FIG. 8B.
As shown in FIG. 5, an insertion part 10 of a conventional clip apparatus for ligaturing a living tissue includes a distal end portion 10a, a proximal end portion 10b, and a passage 10c extending between the distal end portion 10a and the proximal end portion 10b. The insertion part 10 is inserted into a forceps channel of a not-shown endoscope inserted into a body cavity of a living body, for example a living body, with the distal end portion 10a being as a leading end.
In the above conventional clip apparatus, a clip 12 included in a clip unit 14 provided removably at the distal end portion 10a of the insertion part 10 has slender arms 12c having independent distal ends 12a and other ends 12b connected to each other, and is capable of elastically opening and closing the distal ends 12a. 
In the above conventional clip apparatus, a clip operating part 16 being capable of opening and closing the clip 12 of the clip unit 14 includes an external operation portion 16a exposed at the proximal end portion 10b of the insertion part 10 and a clip connecting portion 16b extending in the passage 10c of the insertion part 10 from the external operation portion 16a to the distal end portion 10a of the insertion part 10 and connected to the clip unit 14. And, the clip 12 of the clip unit 14 can be opened and closed by operating the external operation portion 16a. 
In the not-shown endoscope, If the insertion part in which the forceps channel is extending does not have flexibility, each of the insertion part 10 and clip operating part 16 of the clip apparatus may not have flexibility. However, if the insertion part of the not-shown endoscope has flexibility, each of the insertion part 10 and clip operating part 16 of the clip apparatus must have flexibility in order to follow curving of the insertion part of the endoscope.
Next, a configuration of the conventional clip unit 14 will be explained with reference to FIGS. 5, 6A and 6B.
The clip unit 14 comprises a clip holding member 18 whose diameter is smaller than that of an opening of the passage 10c in the distal end portion 10a of the insertion part 10. The clip holding member 18 has a clip projecting/retracting passage 18a which extends along a longitudinal center line of the passage 10c and which holds the clip 12 in a projectable/retractable state. When the clip 12 is projected from and retracted into the clip projecting/retracing passage 18a, outside surfaces of the arms 12c of the clip 12 slidingly contact an inner circumferential surface of the clip projecting/retracting passage 18a so that the arms 12c are elastically opened and closed.
The clip unit 14 further comprises engaging portions 20 which are provided around the clip projecting/retracting passage 18a in the clip holding member 18 and which are radially and elastically openable and closable relative to the clip projecting/retracting passage 18a. Each of the engaging portions 20 is slender in a longitudinal direction of the clip projecting/retracting passage 18a. And, only a distal end of the engaging portion 20 in a direction in which the clip holding member 18 projects from the opening of the passage 10c in the distal end portion 10a of the insertion part 10 is connected to a circumferential wall of the clip holding member 18 while the engaging portion 20 excluding the distal end is separated from the circumferential wall of the clip holding member 18. While the clip holding member 18 is retracted in the opening of the passage 10c in the distal end portion 10a of the insertion part 10, each of the engaging portions 20 is pushed by the inner circumferential surface of the passage 10c and elastically bent (that is, closed) about the distal end radially inward relative to the clip projecting/retracting passage 18a. When the clip holding member 18 projects from the opening of the passage 10c, each of the engaging portions 20 is elastically flipped up (that is, opened) around the distal end radially outward relative to the clip projecting/retracing passage 18a. The rear ends of the elastically opened engaging portions 20, located opposite to the distal ends in the longitudinal direction of the clip projecting/retracting passage 18a, engage with a periphery of the opening of the passage 10c in the distal end portion 10a of the insertion part 10 in a direction along the longitudinal center line of the passage 10c, and prevent the clip holding member 18 from retracting into the opening of the passage 10c in the distal end portion 10a of the insertion part 10.
The clip unit 14 further comprises a connecting member 22 which is provided in the clip projecting/retracting passage 18a of the clip holding member 18 and which is movable in the extending direction of the clip projecting/retracing passage 18a. The connecting member 22 is connected to the proximal end portions 12b of the slender arms 12c of the clip 12 and to the clip connecting portion 16b of the clip operating part 16. The connecting member 22 is operated by the clip operating part 16 to move together with the clip 12 in the above described extending direction in the clip projecting/retracing passage 18a. The connecting member 22 has a breakable portion 22a which is broken when a pulling force larger than a predetermined value is applied thereto by the clip operating part 16.
In the conventional example shown in FIGS. 5, 6A and 6B, two engaging portions 20 are provided at two positions in the clip holding member 18, the two positions being separated from each other by 180° in a circumferential direction of the clip holding member 18 around the clip projecting/retracting passage 18a. The clip holding member 18 and the two engaging portions 20 are formed as one body by injection molding of synthetic resin with appropriate elasticity and high intensity, such as polyphthalamide (PPA), polyamide (PA), and the like.
The connecting member 22 is formed by injection molding of resin material with high intensity, such as liquid crystal polymer, nylon, and the like. The breakable portion 22a is a cut out which is cut from a part of an outer circumferential surface of the connecting member 22 inwardly in a radial direction of the clip holding member 18 and which extends in a direction crossing the extending direction of the clip projecting/retracting passage 18a. In this cut out, the other ends 12b connected to each other in the slender arms 12c of the clip 12 are hooked.
A proximal end portion 22b of the connecting member 22 is branched into two sections, the proximal end portion 22b being closer to the distal end portion 10a of the insertion part 10 than the breakable portion 22a. Two branched sections are close to each other with a radially extending division line 22c interposed therebetween, and a connection hole 22d extending along the longitudinal center line of the clip projecting/retracting passage 18a is formed in closely facing ends of the branched sections. In the connection hole 22d at the two branched sections of the proximal end portion 22b of the connecting member 22, a substantially conically shaped engaging portion 16c of a projecting end of a projection projecting from the distal end of the clip connecting portion 16b of the clip operating part 16 in the longitudinal direction of the clip operating part 16 is pressed in, so that a rotational connection between the two branched sections of the proximal end portion 22b of the connecting member 22 and the clip connecting portion 16b of the clip operating part 16 is achieved.
A part of the outer circumferential surface of the connecting member 22 is flattened, and a part of the inner circumferential surface of the clip projecting/retracting passage 18a of the clip holding member 18, the part corresponding to the flattened part of the outer circumferential surface of the connecting member 22, is also flattened. The flattened part of the inner circumferential surface of the clip projecting/retracing passage 18a extends in a moving range of the flattened part of the outer circumferential surface of the connecting member 22 while the connecting member 22 moves in the clip projecting/retracting passage 18a. As a result, the connecting member 22 does not rotate in the circumferential direction of the clip projecting/retracting passage 18a in the clip projecting/retracting passage 18a. 
A moving path of the breakable part 22a of the connecting member 22 in the clip projecting/extracting passage 18a is adjacent to the inside surface of one of the two engaging portions 20.
Next, a process of ligaturing a desired region of a desired living tissue in a body cavity of a living thing, for example a human body, by using the conventional clip apparatus configured as described above.
First, the insertion part of the not-shown endoscope is inserted into the body cavity, and the distal end of the insertion tube is directed to the desired region of the desired living tissue. Then, the insertion part 10 of the conventional clip apparatus is inserted into the not-shown forceps channel of the endoscope with the distal end portion 10a being as the leading end. In this time, the clip 12 is retracted into the clip projecting/retracting passage 18a of the clip holding member 18, and the clip holding member 18 is retracted into the distal end portion of the passage 10c of the insertion part 10.
After the distal end portion 10a of the insertion part 10 is projected from the distal end opening of the forceps channel of the insertion part of the endoscope, the external operation portion 16a of the clip operating part 16 is pushed to project the clip holding member 18 from the distal end portion of the passage 10c of the insertion part 10 and to project the clip 12 from the clip projecting/retracing passage 18a of the clip holding member 18.
Each of the two engaging portions 20 of the projected clip holding member 18 is elastically flipped up (that is, opened) around its distal end outward in the radial direction of the clip holding member 18, as shown in FIG. 7A. The rear ends of the opened engaging portions 20 are engaged with the periphery of the opening of the passage 10c in the distal end portion 10a of the insertion part 10 in the direction along the longitudinal center line of the passage 10c, and prevent the clip holding member 18 from retracting into the opening of the passage 10c in the distal end portion 10a of the insertion part 10.
As shown in FIG. 7A, the projected clip 12 opens the arms 12c around the other ends 12b outward in the radial direction of the clip projecting/retracing passage 18a. Thereafter, in order to locate the gap between the opened distal ends 12a of the arms 12c of the clip 12 on the desired region DR of the desired living tissue in the body cavity of the living thing, for example the human body, the direction of the distal end portion of the insertion part of the not-shown endoscope (that is, the direction of the distal end portion 10a of the insertion part 10) and the push amount of the external operation portion 16a of the clip operating part 16 directing the proximal end portion 10b of the insertion part 10 (that is, the projecting distance of the clip 12 from the clip projecting/retracting passage 18a of the clip holding member 18) are adjusted.
Then, after the external operation portion 16a is pushed to make the opened distal ends 12a of the arms 12c of the clip 12 bite the desired region DR of the desired living tissue, the external operation portion 16a is pulled while holding the proximal end portion 10b of the insertion part 10 not to move the insertion part 10 in its longitudinal direction. As a result, while the arms 12c of the clip 12 are pulled into the clip projecting/retracting passage 18a of the clip holding member 18, the outside surfaces of the arms 12c slidingly contact the periphery of the opening of the clip projecting/retracing passage 18a at the projecting end of the clip holding member 18 and are pushed inward in the radial direction of the opening, so that the distal ends 12a of the arms 12c of the clip 12 can hold the desired region DR of the desired living tissue, as shown in FIG. 7B.
By pulling the external operation portion 16a furthermore, a pulling resistance generated in the desired region DR of the desired living tissue and a frictional resistance generated on the outside surface of the arms 12c of the clip 12 with respect to the periphery of the opening of the clip projecting/retracing passage 18a are increased, so that the pulling force applied to the base of the breakable portion 22a of the connecting member 22 by the clip operating part 16 gets close to a predetermined value at which the base of the breakable portion 22a is to be broken.
Just before the base of the breakable portion 22a of the connecting member 22 is broken, a deviating force BF around the base is applied to a distal end portion 22e of the connecting member 22, as shown in FIG. 7C.
In a case that the opening distance of the distal ends 12a of the arms 12c of the clip 12 is relative large when the opened distal ends 12a of the arms 12c of the clip 12 bites the desired region DR of the desired living tissue as shown in FIG. 7B, the deviating force BF around the base is applied to the distal end portion 22e of the connecting member 22 as shown in FIG. 7C before the arms 12c of the clip 12 are sufficiently pulled into the clip projecting/retracting passage 18a of the clip holding member 18.
In this time, the distal end portion 22e of the connecting member 22 faces the inside surface of one of the two engaging portions 20 of the clip holding member 18 in the clip projecting/retracing passage 18a. Therefore, the distal end portion 22e of the connecting member 22 to which the deviating force BF is applied pushes the inside surface of the engaging portion 20 corresponding to the distal end portion 22e of the connecting member 22 outward in the radial direction of the clip projecting/retracting passage 18a, until the base of the breakable portion 22a of the connecting member 22 is broken as shown in FIG. 7D.
As a result, the arms 12c of the clip 12 are prevented from being pulled furthermore into the clip projecting/retracting passage 18a of the clip holding member 18, so that the bite of the distal ends 12a of the arms 12 of the clip 12 in the desired region DR of the desired living tissue (that is, the ligaturing of the desired region DR of the desired living tissue) is left insufficiently.
In addition to the conventional clip apparatus described above with reference to FIGS. 5 to 7D, another conventional clip apparatus is known. The other conventional clip apparatus is only different from the above described conventional clip apparatus in that a direction RO in which the engaging portion 20 close to the base of the breakable portion 22a of the connecting member 22 in the clip holding member 18 bends elastically is displaced in the circumferential direction of the clip holding member 18 by 45° from a direction in which the deviating force BF around the base applied to the distal end portion 22e of the connecting member 22 just before the base of the breakable portion 22a of the connecting member 22 is broken, as shown in FIGS. 8A and 8B.
Even in such the other conventional clip apparatus, the same problems as that occurred in the conventional clip apparatus described above with reference to FIGS. 5 to 7D are occurred.